Hi,
I had to redirect the registration 'Sign Up' link from the preset Joomla to the Jomsocial one, here is how I did it if it helps anyone with the same issue...
I found the file to replace the joomla registration link with your jomsocial one.
/templates/gk_msocial/layouts/default.php
Find this line and change the link to your jomsocial one (The link bit is in bold)
<a href="<?php echo JRoute::_('index.php?option=com_users&view=registration'); ?>" id="gkRegister"> <?php echo JText::_('TPL_GK_LANG_REGISTER'); ?></a>
Take a backup of the file first in case you notice any other issues, then you have it to re-upload
There is also the register link on the popup login window to change, will post when I find it...
Respect,
Marc